It is planned to investigate the chemical modification of the C-nucleoside antibiotic Showdomycin, per se. A carefully designed program which will involve functional group transformations of both the heterocyclic and carbohydrate moieties of showdomycin will be initiated in an effort to potentiate the marginal antitumor activity reported for showdomycin. We also propose to synthesize several showdomycin derivatives which will be designed not only as potential antitumor agents but also as potential antiviral agents. Studies will also be undertaken which should provide considerable insight into the relationship between the structure, conformation and stability of these showdomycin derivatives and their biological and chemotherapeutic activity. The current information would indicate that a carefully planned program involving the synthesis of specific nucleosides from showdomycin should provide compounds which could be used for evaluating the validity of the reported mode of action for showdomycin. The nucleosides prepared under this program will be evaluated as antiviral agents and additional information concerning their biological activity and mode of action will be obtained in direct collaboration with biochemists, pharmacologists, biologists and microbiologists at various institutions and universities. Nucleosides prepared in this study and designed specifically as potential antitumor agents will also be evaluated for cytotoxicity against L-1210 in vitro in our laboratory and in the National Cancer Institute program in vivo.